A Jewish New Yorker and his Cambodian-born college friend walk into a sandwich shop. No, this isn't the beginning of a bad joke, it's the story behind Num Pang, the much loved sandwich cafe with locations in Greenwich Village and Midtown.

Ratha Chaupoly and Ben Daitz met in college, but reconnected years later after they both worked in the culinary world. Today, they are the owners and driving forces behind both locations and have plans to launch a third shop later this year. Num Pang has been widely praised by critics and continues draw large crowds on a daily basis. Chaupoly and Daitz have also previously teamed up with chefs Mario Batali, Dan Kluger and Floyd Cardoz to create limited edition sandwiches specifically for Num Pang. Yesterday, the restaurant's owners sat down with Fork in the Road to discuss their success, Cambodian culinary traditions, and why they'll never accept substitutions.

Tell me how you got started.Ratha Chaupoly: I've been in this business 18 years. I was born in Cambodia but I didn't move here until I was 9. I started my career in the front of the house and decided to open up my own place. I wanted to do Cambodian food but I couldn't find anybody in the kitchen that was thinking the same way as me. I wanted to move the food forward a bit. [Cambodian] culture -- what's available there foodwise, the equipment, the knowledge -- is still 30 years behind, if not a bit more. So I thought, "How can I bring my country's food to the now?" So I jumped in the kitchen. That was probably six or seven years ago.

Do you ever feel confined by the traditions in which Cambodian food is rooted?RC: I'm respectful of the traditions through the ingredients and the flavors. But if you can tweak the techniques and marry combinations without having to abuse the flavors, that's the most important thing. I don't feel confined or restricted. I respect that, generation after generation, Cambodians cook the same things. It's like being a musician. If you play the same beat over and over, it's actually harder than if you went all crazy.

And Ben, how do you feel about working with flavors that are specific to Ratha's personal heritage and not yours?Ben Daitz: What? You're talking crazy. I'm Cambodian. Ratha's Jewish and from the Upper West Side. [Laughs] Our food is far from strict Cambodian cuisine. As far as I see it, I take my training and apply different flavors and different techniques to our food. Nobody is saying it's not strictly Cambodian enough, or that it's not working.

RC: Yea, my mom is not here whipping us.

You've been widely praised in the press. I could barely find any negative reviews of either of your locations--RC: Why were you looking at that? [Laughs] We just put so much work into every item on the menu. Our shop gives people enjoy the food of a two star restaurant in a fast casual environment. It's not just [putting out] sandwiches. This is a meal.

You're well known for your fierce no substitutions policy. People order what's on the menu and that's what they get. The first time I came here, I expected a Soup Nazi-style experience.BD: Did you look straight ahead and have your money out?

Yes, exactly. Do you apply that policy to the rest of your life?RC: Yes!

BD: Well, that's a little personal. But I do. Don't ever accept anything less than what you want.

Has anyone ever completely lost it over the inability to make changes to their order?BD: Oh yeah. People want to fight. In the beginning, there was this guy who got into it because his girlfriend didn't want carrots...

RC: And then there's been one recently who didn't want cilantro. It's either carrots or cilantro, those are the two main things that people don't want. Those ingredients just start unnecessary things.

BD: That's part of the reason why we stopped being cashiers. As much as we love interacting with the customers, after a while we realized we should hire some even-keeled, nice, well-rested people to deal with them.

Check back tomorrow to hear what Chaupoly and Daitz have to say about working together, celebrity chef collaborations, and which of their sandwiches is Num Pang's best.